In many industrial applications, it is desirable to measure the torque applied to a rotating shaft. These torque measurements can be utilized in shaft design in order to provide optimal strength and predict failure thereof. U.S. Pat. No. 4,637,264 discloses an optical torque detector in which a pair of rotary plates are utilized, each having a radial optical grid disposed so as to face one another and which are connected to a shaft member, of which the torsional torque is to be detected. The plates are separated by a predetermined spacing between their connected positions to the shaft so that a Moire fringe pattern may be created in accordance with change of a relative turning between the rotary plates caused by torsion of the shaft member. A detecting device is provided for detecting a shift of the MOIRE fringe pattern so that a torsional torque of a shaft member may be detected. This type of torque detecting device is limited to detection of torque across a unitary shaft, and requires the design of a complex Moire fringe pattern. Accordingly, it is desirable in the art to provide a less complex method of torque detection for a rotating shaft. Furthermore, it is desirable to allow for easy switching between different load ranges by replacing a flexible element to provide a wider range of torque detection.
According to one aspect of the present invention, a torque detector is provided including a torque input element, a spring element connected to the torque input element, a torque output element connected to the spring element, and a sensing system for sensing a rotational offset between the torque input element and torque output element. The spring element is designed to be replaceable with different spring elements in order to allow detection of different load ranges.
According to another aspect of the present invention, a light emitting device is provided along with a first toothed member connected to the torque input element and a second tooth member connected to the torque output element. A light sensing device is disposed on the second side of the first and second toothed members opposite the light emitting device wherein a processor is utilized for processing a signal from said light sensing device for determining an average signal level and associating said average signal level with a corresponding torque level.
According to yet another aspect of the present invention, a first magnetic encoder member is connected to the torque input element and a second magnetic encoder member is connected to the torque output element, wherein a sensing system is provided for simultaneously determining a rotational position of the first and second magnetic encoders and determining a rotational offset therebetween and associating the determined rotational offset with a corresponding torque level. In further alternative arrangements, a capacitance-based sensing system and a linear variable displacement transformer-based sensing system are also disclosed.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.